English: Fenite from the Devonian of Russia.

Fenite is a rare variety of metasomatite, a metamorphic rock formed solely by chemical alteration of previously existing rocks. The type locality for this lithology is the Ediacaran to Cambrian-aged Fen Carbonatite Complex in Norway. Fenites occur next to carbonatite complexes and form by CO2 chemical alteration.

This fenite sample is from northwestern Russia's Lovozero Alkaline Massif (Late Devonian, ~360 to 370 Ma). The dark gray matrix is the fenite. Three minerals occur in the sample as large crystals embedded in fenite: 1) murmanite (= buff-colored blocky crystal at top), a rare hydrous sodium titanium silicate (Na2Ti2(Si2O7)O2·2H2O); 2) aegirine (= long, slender black sticks), a type of pyroxene, sodium iron silicate (NaFeSi2O6); and 3) eudialyte (= reddish-purplish colored masses), a rare complex silicate mineral whose formula varies from reference to reference (for example, Na4(Ca,Ce)2(Fe,Mn,Y)ZrSi8O22(OH,Cl)2).

Locality: Selsurt Mountain (= Flora Mountain), Lovozero Massif, Kola Peninsula, far-northwestern Russia

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See more info. at:

Murmanite: www.mindat.org/min-2813.html

Aegirine: www.mindat.org/min-31.html

Eudialyte: www.mindat.org/min-1420.html

Lovozero Alkaline Massif: www.mindat.org/loc-2697.html and en.wikipedia.org/wiki/Lovozero_Massif and en.wikipedia.org/wiki/Kola_Alkaline_Province and

Mikhailova et al. (2019) - Petrogenesis of the Eudialyte Complex of the Lovozero Alkaline Massif (Kola Peninsula, Russia). Minerals 2019(9)(10)(581). 31 pp. (www.mdpi.com/2075-163X/9/10/581)